This invention is based on the discovery of flame retarded reinforced molding compositions of poly(1,4-cyclohexlene dimethylene terephthalate), sometimes referred to herein as PCT, or high melting crystalline copolymers thereof with improved mechanical properties. Generally, polyesters are flame retarded by using halogenated organic compounds in combination with antimony oxide.
Polyesters have been used as engineering plastics for mechanical parts of various machines, electrical equipment and parts of motor cars. Preferably, engineering plastics are provided with fire-proof properties, that is the flame retardancy, in addition to well-balanced ordinary physical and chemical properties. Such properties are indispensable in thermoplastic polyesters in order to enlarge their use as engineering plastics, because they are normally used at temperatures higher than 100.degree. C.
Generally speaking, the flame retarding agents deteriorate the original physical properties of the base polymer, and therefore it is of importance to find a good combination of organic polymer and flame retarding agent. In respect to polyesters, several methods have been proposed. The use of antimony oxide in combination with brominated organic compounds is well known in the art of flame retarded polymers. Sodium antimonate used in combination with brominated organic compounds and used as a replacement for antimony oxide to flame retard poly(ethylene terephthalate) is disclosed in U.S. Pat. No. 4,338,243.
Japanese Patent Publication (Kokai) No. 46-2086 discloses combined use of decabromodiphenyl and antimony trioxide as a flame retarding agent. According to this method it is possible to give reduced flammability to a glass fiber reinforced polyester resin, but the polyester composition thus obtained is not satisfactory in many physical properties, especially heat deflection temperature, which is essential in certain applications such as electrical circuit boards, etc.
The superior improved moldability and improved properties of the molded article obtained by reinforcing poly(alkylene terephthalate) resins such as poly(ethylene terephalate) (PET) and poly(cyclohexylene dimethylene terephthalate) (PCT) has long been established (see e.g., U.S. Pat. No. 3,814,725).
It has long been known that specific nucleating agents and plasticizers when added to PET reinforced with glass fibers enhance the moldability of the composition in molds heated from 90.degree. C. to 150.degree. C. Patents relating to the use of dibenzoates in polyesters include U.S. Pat. Nos. 4,172,824, 3,516,957, 4,368,285, 4,223,125, 4,357,268, 4,506,050, 4,483,955, 4,440,889, 4,451,606 and 4,548,978.
Other additives of interest are disclosed in U.S. Pat. Nos. 4,357,268, 4,385,144, 4,486,561, 4,539,352 and 4,551,485. These include additives such as polyepoxides prepared from bisphenol A and epichlorohydrin, epoxidized plasticizers and organofunctional silane coupling agents.
In addition, U.S. Pat. No. 3,962,174 describes an improved thermoplastic molding resin comprising reinforced poly(butylene terephthalate) or poly(propylene terephthalate) polymers in the presence of a thermoplastic phenoxy resin.
Also, U.S. Pat. No. 4,008,199 describes stabilized poly(alkylene terephtalatate) resin compositions comprising poly(propylene terephthalate) or poly(butylene terephthalate), a reinforcing filler and a stabilizing amount of a mixture of a polyamide polymer, a phenoxy resin and an organic phosphonate.
However, there is still a need for reinforced polyesters for use in injection molding applications such as in the production of automotive and electronic parts, which have good flame retardancy as well as good mechanical and physical properties.
A problem which has existed in the past is that when flame-retarding compounds are added to reinforced molding compositions, physical properties are adversely affected. It has now surprisingly been found that when the combination of additives according to the present invention are used, flame retardant properties are achieved without the usual loss of physical properties of the molding compositions.
Copending application Ser. No. 086,997 filed Aug. 19, 1987, now U.S. Pat. No. 4,778,820, issued Oct. 18, 1988, relates to the use of a combination of powdered antimony metal with the conventionally used brominated organic compounds.
Also, copending application Ser. No. 041,505 filed Apr. 23, 1987 relates to the incorporation of a phenoxy compound in a reinforced polyester of terephthalic acid and 1,4-cyclohexanedimethanol.